General information on certain minerals whose utilization is growing or tending to grow

UNITED NATIONS

ECONOMIC

SOCIAL COUNCIL AND

LIMITED

E/CN.14/MIB/1

12 December 1967 ORIGINAL: FRAffCAIS

1

Economic Commission for Africa Seminar on New Metals and Minerals Addis Ababa, 5-10 February 1968

GENERAL INFORMATION ON CERTAIN MINERALS WHOSE UTILIZATION IS

GROWING OR TENDING TO GROW

(submitted by the Government of Rwanda)

M68-1

GENERAL INFORMATION OH CERTAIN MINERALS WHOSE UTILIZATION IS GROWING OR

TENDING TO GROW

N. Nda-Ruhutse

Introduction

Mining, is one of the main bases of the economic development of Rwanda.

It employs more-wage earners than any other industry and takes second place

in exports after agriculture.

Nevertheless, the mineral wealth of Rwanda comprises a fairly small number of substances• The minerals which have been worked since the origin of mining in Rwanda in about 1930, are cassiterite, wolfram, colombo-tantalite,

beryl, amblygonite, gold and bismuth. Monazite, although discovered quite early, has not yet been worked.

More or less certain indications exist for the ores of Cu,- Pb, Zn, Th

and various rare earths, but the size and workability of the -deposits have

not yet been determined. A large research project has been undertaken to permit the maintenance and development of the existing mining industry, the working of known deposits that are not mined to any great extent, such as

beryl and amblygonite, exploration for substances for which there are only

,, indications, that is, whose existence is known: uranium, copper, zinc, lead,

primary gold, carbonatite, peat containing monazite, clays for ceramics, special volcanic materials, as well as the search for new'substances for which there are very few indications but which have increasing applications

in modern industry.

Of these new and rare minerals we shall mention here those which are known, giving particular prominence in each case to those which have been

found in Rwanda.

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We shall speak ofi

1. Minerals and ores of the rare earths associated

with cerium:

yttrium, europium, gadolinium, ytterbium, neodymium,

praseodymium, lanthanium ... ;

2. Beryl .

3. .Colombite and colombo-tantalite;

A* Titanium;

5» Minor minerals or ores.

1# Minerals and ores of rare earths associated with cerium

The two principal ores of cerium are monazite, present in Rwania in the alluvium to the west of Butare, and bastnaeeite, a complex carbonata, present in Burundi in a primary pegmatite deposit worked by Somuki.

Small quantities of monazite and bastnaesite occur with other

ores, sometimes in association; this is especially the case with bastnaesite, known by the generic term of "rare earths".

In Rwanda, monazite qccurs with hematite, zircon and ilmenite in

the form of non-workable traces.

It is concentrated, mainly in alluvium so that its origin can be traced to a degradation by erosion of the granite massifs of the Rusizi system. Another possible origin is the numerous veinlets of quartz whioh intersect the rocks in several places.

The uses of the rare-earths in electronics, optics, the nuclear industry, and sometimes in chemistry, are well known.

World consumption is now of the order of 2,300 tons of oxido concentrates. We shall cite the corresponding metals in order of importance, yttrium being well in the lead with more than half of the

total indicated.

a) Like eurcpium and gadolinium, yttrium has applications in

the colour television industry, notably for tubes. The oxide of

high purity has nuclear applications. It is also used for polishing

high precision optical lenses, and certain types of mirrors.

It can also be used in the colour industries. It is used in metallurgy for very special alloys, and in certain petroleum cracking towers in which it notably improves the recovery yield by facilitating catalysis. Yttrium oxide is worth $42 - 45 per lb, according to the degree of purity. Yttrium metal is worth $75-300 per lb. After double distillation, its price is $500 per It.

The oxide of europium is valued at $1,000 per lb.

Europium metal is valued at. $1,200 - 3,500 per lb.

^) Other rare metals

-These are utilized chiefly for their luminescent properties.

Along with europium, already mentioned, we find terbium, neodymium and praseodymium. The principal applications are in the optical, the cut glass, and some plastics industries. ■

Research is being actively pursued on these products which have reoently been isolated by chenistry, and new applications may

be espected. . . -

Certain radio-isotopes such as ytterbium 16$ are used-in radio graphy! others are used in the treatment of-cancerous tumors.

c) Cerium ■ '

.. This is extracted principally from monazite, and to some extent from bastnaesite. It is used especially in the manufacture of lighter flints, thanks to its very marked pyrophoric properties.

Monazite is obtained chiefly from beach deposits on the coasts of Australia, Brazil and India. Its price is about $200-500 per ton,

according to grade.

Treated chemically, the compounds obtained have a much higher

value:

• Pure hydrate of cerium sells in 100 lb lots at Sl.45-l.70

per lb« ...

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Pure cerium oxide for optical uses sells in 50 lb lots at

$1.90 per It. Cerium oxide of high purity is sold at $9 per lb, while

cerium metal (99.9 per cent) sells for $70 per lb.

2. Beryl

The principal ore of beryllium is a complex silicate called beryl, found in sodolithic pegmatites in the rock form: this ore is worked in Rwanda in the Congo-Nile watershed. (The average annual production is 150 tons).

In the form of gems, it constitutes a highly-valued jewellery stone- aquamarine, smsrald, morganite, etc. - that does net seem to have been found

in Rwanda.

The BeO content of rock beryl is of the order of 10-12 per cent.

Prices are variable, according to-the tenor, the order of magnitude being

$250 per tnn.

. . Consumption is about 10,000 tons per year. ' Beryl oxide powder

(20 mesh) is worth «1O-15 per lb. Beryllium'metal (97 per'cent) is valued

at $62 per pound in lots of 1,000-2,000 lb. The applications of beryl are

numerous, but the treatment for obtaining powdered oxide, oxide of nuclear purity, and the metal, is complicated and expensive. The oxide of nuclear purity is used as a moderator in atomic reactors, especially in France and the United States. In this field, its uses derive from its great.stability;

its power of reflecting and moderating nuclear reactions rank it with graphite and heavy water, but its low weight leaves it without competition for the construction of nuclear propelling engines.

Beryllium oxide is an excellent refractory, used in spark-plugs of aircraft engines, high frequency insulators,"and combustion chambers, etc.

There are also alloys having.very special applications for certain mechanical parts, such as helicopter rotors and submarine screws.

We should note in passing the Cu-Be alloys, which have high resistance to fatigue and wear, the heat-resistant Cu-Co-Be alloys, etc.

3- Columbite and columbo-tantalite

There are three kinds of ores:

The colum"bites with a ver;> high proportion of niobium, tantalite being present only in very small quantites.

This is the Mgerian t;ype of ore.

The columbo-tantalites, in which the proportions of niobium and tantalum are variable, but in the relatively high ratios of 1:3 and 3:1. This ore is often associated with cassiterite, or even with beryl in certain granite pegmatites. In Rwanda, the proportion of tantalum is almost equal to that of niobium, sometimes even a little higher. Production is about 60 tons and can doubtless be increased, if the explorations planned lead to the discovery of new reserves.

The tantalites are ores of tantalum in which the proportion of niobium falls below 33 per cent. It is a much sought- after but very rare ore. Indications have been reported in the north-east of the country, but the tenors in tapiolite especially have proved to be so low that the deposits have never been worked.

Prices vary according to the type of ore; for example, the columbites have a maximum price when the ratio of the oxides Fb 205

is higher than 10:1, In this case the ore is priced at $0.90

to n.00 per lb of oxide content (1964 price). When the ratio :fe

is higher than 3:1 the quotation is on the basis of tantalite. In this case, the ore is priced at &3-&4.50 per lb of oxide content

(I964 price).

The intermediate ores, that is, the so-called columbo-tantalites, are priced individually by lot. World production is of the order of 5,000 tons, of which 4,000 tons consists of columbites. The two principal producers of columbite are Canada and Nigeria, with more than 90 per cent of the world total. Brazil ie the principal producer of tantalite.

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The main applications of niobium and tantalum are in the space and

aeronautical industry. They aro used in the form of special alloys resistant to very hi.3h tarnperatures, in the construction of jet and rocket engines. A, present the tendency is tc use them with metals

like zirconium and titanium.

4« Titanium

The two principal ores of titanium are ilmenito and rutile.

Ilmenxte, like monazite, is obtained chiefly from beach sands (so-called Mack sands"), and oo.es principally fro, Canada, Australia and India.

Rutile is obtained mostly from Australia, and to a smaller extent from Portugal, India, Senegal and the United States.

Ilmenite is an ore containing of 59.5 pE,r cent TiO .

Eutile is an ore of 94 pG1- oent TiO . 2

The main applications of ilmenite are in the fabrication of titanium metals, in the ceron.utical i^stry and space research. It is a metal resistant to very hieh temperatures. World consumption is of

theorder of 2 = 5 raillio

^{^}

t

^toDS

h

Eutile, with a production of the order of 200,000 tons, has a very wide range of application, in the paint industry (titaniun, white) aB

-11 as in ,allPapB, and pi^tic, ' Consumption is increasing at the same

rate as for ilmcnito,

Prices FOB iUlantio ports are, respectively. •

123-^6 per l.ms ton, for ilmenite of. ^.5 per cent TiO . 1104 per ohor'. ton for rutile of 94 per cent TiO . 2

Prices of the metal are:

(In lots of 10,000*lb)

Sponge 99-3^ titanium ' Si.32 -e per lb

Sheet :M-9O-5aO per lb

5- .Minor oreg^ncMniTi ora, 1b

This category it mentioned only as a curiosity for most of these substances are secondary m3tals recovered in the treatment of other metals;

for example, galliu,, a by-produ,t of alurainium production; germanium, a

by-product of zinc production; rhenium, h by-product of molybdenum production, selenium and tellurium, by-products of electrolytic copper production, other sub-forms of very special compounds deposited in saline lagoon formations, and cesium .and rubidium, which are some-times found in

very special pegmatites (scandium).

Conclusions "

"With regard to the minerals or.ores mentioned in.this note, it

appears that: . . . . ■■ ■: ■■-•.-.

Monazite is present in the small flats-to the south of Gikongoro and analyses of the crude product are essential to assess the value of the deposits and especially to see if it is associated with rare

minerals that might raise the sales price (particularly yttrium);

this has not yet been demonstrated.

The presence of bastnaesite has not been established so far but

it cannot be -excluded a priori; the United Nations project should remove the doubt;

Beryl is present in the watershed in some thirty fairly large pegmatite deposits and in certain deposits worked by diggers;

recovery is by hand-picking, the only known method suited to the special conditions of the deposit;

Columbo-tantalites are present, often associated with cassiterite;

the market trend is £ood for products rich in tantalum, and working- should be promoted as much as possible wherever the combiffied value of the cassiterite plus columbo-tantalite content is adequate;

Rutile has not been prospected for, but its value is insufficient to justify even "artisanal" exploration and working, the transport

cost being much too high in relation to the FOB value of the product;

The minor ores mentioned are not yet represented, and there are only theoretical probabilities in connexion with possible deposits of copper, lead or zinc, or even uranium, of which there are some positive indications.

E/CN.14/MIN/1

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The systematic analysis of all types of samples, from all sources, is the only way of producing convincing evidence to

justify mining, but the implementation of the project submitted for approval to the United Nations must be awaited for this.

It should also be noted in passing that other products may be of interest for local utilization-peat as a ft.al, gas as raw material for onergy and reduction, and limestone and lava for cement - and finally tha- the discovery of several individually non-workable deposits of heavy substances (such as amblygonite, manganese and chromite) might lead to a modification of transport facilities as to render the working of such

products economic.